Fine structure characterization of zero-valent iron nanoparticles for decontamination of nitrites and nitrates in wastewater and groundwater

The main objectives of the present study were to investigate the chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization. This work also exemplifies the utilization of field emission-scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD) to reveal the speciation and possible reaction pathway in a very complex adsorption and redox reaction process. Experimentally, ZVIN of this study was prepared by sodium borohydride reduction method at room temperature and ambient pressure. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20-50 nm were observed with FE-SEM or TEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65-83% and 51-68%, respectively, based on three different initial concentrations. Based on the XRD pattern analyses, it is found that the quantitative relationship between nitrite and Fe(III) or Fe(II) is similar to the one between nitrate and Fe( III) in the ZVIN study. The possible reason is due to the faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The extended x-ray absorption fine structure (EXAFS) or x-ray absorption near edge structure (XANES) spectra show that the nitrites or nitrates reduce to N-2 or NH3 while oxidizing the ZVIN to Fe2O3 or Fe3O4 electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive

Oxidation Kinetics of the Combustible Fraction of Construction and Demolition Wastes

ABSTRACT The composition of CDW is variable, including dirt, stones, bricks, block, concrete, steel, glass, plaster, lum- Proper disposal of construction and demolition wastes (CDW) has ber, shingles, plumbing, heating, and electrical parts received wide attention recently due to significantly large quantities of tron microscopy-energy dispersive spectroscopy (SEM-EDX). The Construction and demolition waste streams generally ash streams were identified as nonhazardous materials based on the contain 10 to 15% combustible materials, such as wood, toxicity characteristic leaching procedure (TCLP). Overall, the scientific findings gained in this study will be helpful for supporting a sound wallpaper, plastics, and rubber (Gavilan and Bernold, engineering design of real-world CCDW incineration systems. 1994

Dynamics of HBV cccDNA expression and transcription in different cell growth phase

<p>Abstract</p> <p>Background</p> <p>The covalently closed-circular DNA (cccDNA) of hepatitis B virus (HBV) is associated with viral persistence in HBV-infected hepatocytes. However, the regulation of cccDNA and its transcription in the host cells at different growth stages is not well understood.</p> <p>Methods</p> <p>We took advantages of a stably HBV-producing cell line, 1.3ES2, and examine the dynamic changes of HBV cccDNA, viral transcripts, and viral replication intermediates in different cellular growth stages.</p> <p>Results</p> <p>In this study, we showed that cccDNA increased suddenly in the initial proliferation phase of cell growth, probably attributable to its nuclear replenishment by intracellular nucleocapsids. The amount of cccDNA then decreased dramatically in the cells during their exponential proliferation similar to the loss of extrachromosomal plasmid DNA during cell division, after which it accumulated gradually while the host cells grew to confluency. We found that cccDNA was reduced in dividing cells and could be removed when proliferating cells were subjected to long term of lamivudine (3TC) treatment. The amounts of viral replicative intermediates were rapidly reduced in these proliferating cells and were significantly increased after cells reaching confluency. The expression levels of viral transcripts were increased in parallel with the elevated expression of hepatic transcription factors (HNF4α, CEBPα, PPARα, etc.) during cell growth confluency. The HBV transcripts were transcribed from both integrated viral genome and cccDNA, however the transcriptional abilities of cccDNA was less efficient then that from integrated viral genome in all cell growth stages. We also noted increases in the accumulation of intracellular viral particles and the secretion of mature virions as the cells reached confluency and ceased to grow.</p> <p>Conclusions</p> <p>Based on the dynamics of HBV replication, we propose that HBV replication is modulated differently in the different stages of cell growth, and can be divided into three phases (initial proliferation phase, exponential proliferation phase and growth confluency phase) according to the cell growth curve. The regulation of cccDNA in different cell growth phase and its importance regarding HBV replication are discussed.</p

First-time comparison between NO2 vertical columns from GEMS and Pandora measurements

The Geostationary Environmental Monitoring Spectrometer (GEMS) is a UV&ndash;visible spectrometer onboard the GEO-KOMPSAT-2B satellite launched into geostationary orbit in February 2020. To evaluate GEMS NO2 column data, comparison was carried out using NO2 vertical column density (VCD) measured using direct-sunlight observations by the Pandora spectrometer system at four sites in Seosan, South Korea, during November 2020 to January 2021. Correlation coefficients between GEMS and Pandora NO2 data at four sites ranged from 0.35 to 0.48, with root mean square errors (RMSEs) from 4.7 &times; 1015 molec. cm-2 to 5.5 &times; 1015 molec. cm-2 for cloud fraction (CF) &lt; 0.7. Higher correlation coefficients of 0.62&ndash;0.78 with lower RMSEs from 3.3 &times; 1015 molec. cm-2 to 4.3 &times; 1015 molec. cm-2 were found with CF &lt; 0.3, indicating the higher sensitivity of GEMS to atmospheric NO2 in less-cloudy conditions. Overall, GEMS NO2 column data tend to be lower than those of Pandora due to differences in representative spatial coverage, with a large negative bias under high-CF conditions. With correction for horizontal representativeness in Pandora measurement coverage, the correlation coefficients range from 0.69 to 0.81 with RMSEs from 3.2 &times; 1015 molec. cm-2 to 4.9 &times; 1015 molec. cm-2 were achieved for CF &lt; 0.3, showing the better correlation with the correction than that without the correction.</p

First-time comparison between NO2 vertical columns from Geostationary Environmental Monitoring Spectrometer (GEMS) and Pandora measurements

The Geostationary Environmental Monitoring Spectrometer (GEMS) is a UV-visible (UV-Vis) spectrometer on board the GEO-KOMPSAT-2B (Geostationary Korea Multi-Purpose Satellite 2B) satellite launched into a geostationary orbit in February 2020. To evaluate the GEMS NO2 total column data, a comparison was carried out using the NO2 vertical column density (VCD) that measured direct sunlight using the Pandora spectrometer system at four sites in Seosan, South Korea, from November 2020 to January 2021. Correlation coefficients between GEMS and Pandora NO2 data at four sites ranged from 0.35 to 0.48, with root mean square errors (RMSEs) from 4.7×1015 to 5.5×1015 molec. cm−2 for a cloud fraction (CF) &lt;0.7. Higher correlation coefficients of 0.62–0.78 with lower RMSEs from 3.3×1015 to 5.0×1015 molec. cm−2 were found with CF &lt;0.3, indicating the higher sensitivity of GEMS to atmospheric NO2 in less cloudy conditions. Overall, the GEMS NO2 total column data tended to be lower than the Pandora data, owing to differences in the representative spatial coverage, with a large negative bias under high CF conditions. With a correction for horizontal representativeness in the Pandora measurement coverage, correlation coefficients ranging from 0.69 to 0.81, with RMSEs from 3.2×1015 to 4.9×1015 molec. cm−2, were achieved for CF &lt;0.3, showing a better correlation with the correction than without the correction.</p

An Overview of Regional Experiments on Biomass Burning Aerosols and Related Pollutants in Southeast Asia: From BASE-ASIA and the Dongsha Experiment to 7-SEAS

By modulating the Earth-atmosphere energy, hydrological and biogeochemical cycles, and affecting regional-to-global weather and climate, biomass burning is recognized as one of the major factors affecting the global carbon cycle. However, few comprehensive and wide-ranging experiments have been conducted to characterize biomass-burning pollutants in Southeast Asia (SEA) or assess their regional impact on meteorology, the hydrological cycle, the radiative budget, or climate change. Recently, BASEASIA (Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment) and the 7-SEAS (7- South-East Asian Studies) Dongsha Experiment were conducted during the spring seasons of 2006 and 2010 in northern SEA, respectively, to characterize the chemical, physical, and radiative properties of biomass-burning emissions near the source regions, and assess their effects. This paper provides an overview of results from these two campaigns and related studies collected in this special issue, entitled Observation, modeling and impact studies of biomass burning and pollution in the SE Asian Environment. This volume includes 28 papers, which provide a synopsis of the experiments, regional weatherclimate, chemical characterization of biomass-burning aerosols and related pollutants in source and sink regions, the spatial distribution of air toxics (atmospheric mercury and dioxins) in source and remote areas, a characterization of aerosol physical, optical, and radiative properties, as well as modeling and impact studies. These studies, taken together, provide the first relatively complete dataset of aerosol chemistry and physical observations conducted in the sourcesink region in the northern SEA, with particular emphasis on the marine boundary layer and lower free troposphere (LFT). The data, analysis and modeling included in these papers advance our present knowledge of source characterization of biomass-burning pollutants near the source regions as well as the physical and chemical processes along transport pathways. In addition, we raise key questions to be addressed by a coming deployment during springtime 2013 in northern SEA, named 7-SEASBASELInE (Biomass-burning Aerosols Stratocumulus Environment: Lifecycles and Interactions Experiment). This campaign will include a synergistic approach for further exploring many key atmospheric processes (e.g., complex aerosol-cloud interactions) and impacts of biomass burning on the surface-atmosphere energy budgets during the lifecycles of biomass burning emissions

The Non-Catalytic Carboxyl-Terminal Domain of ARFGAP1 Regulates Actin Cytoskeleton Reorganization by Antagonizing the Activation of Rac1

The regulation of the actin cytoskeleton and membrane trafficking is coordinated in mammalian cells. One of the regulators of membrane traffic, the small GTP-binding protein ARF1, also activates phosphatidylinositol kinases that in turn affect actin polymerization. ARFGAP1 is a GTPase activating protein (GAP) for ARF1 that is found on Golgi membranes. We present evidence that ARFGAP1 not only serves as a GAP for ARF1, but also can affect the actin cytoskeleton.As cells attach to a culture dish foci of actin appear prior to the cells flattening and spreading. We have observed that overexpression of a truncated ARFGAP1 that lacks catalytic activity for ARF, called GAP273, caused these foci to persist for much longer periods than non-transfected cells. This phenomenon was dependent on the level of GAP273 expression. Furthermore, cell spreading after re-plating or cell migration into a previously scraped area was inhibited in cells transfected with GAP273. Live cell imaging of such cells revealed that actin-rich membrane blebs formed that seldom made protrusions of actin spikes or membrane ruffles, suggesting that GAP273 interfered with the regulation of actin dynamics during cell spreading. The over-expression of constitutively active alleles of ARF6 and Rac1 suppressed the effect of GAP273 on actin. In addition, the activation of Rac1 by serum, but not that of RhoA or ARF6, was inhibited in cells over-expressing GAP273, suggesting that Rac1 is a likely downstream effector of ARFGAP1. The carboxyl terminal 65 residues of ARFGAP1 were sufficient to produce the effects on actin and cell spreading in transfected cells and co-localized with cortical actin foci.ARFGAP1 functions as an inhibitor upstream of Rac1 in regulating actin cytoskeleton. In addition to its GAP catalytic domain and Golgi binding domain, it also has an actin regulation domain in the carboxyl-terminal portion of the protein

Transforming Growth Factor-β1 Suppresses Hepatitis B Virus Replication by the Reduction of Hepatocyte Nuclear Factor-4α Expression

Several studies have demonstrated that cytokine-mediated noncytopathic suppression of hepatitis B virus (HBV) replication may provide an alternative therapeutic strategy for the treatment of chronic hepatitis B infection. In our previous study, we showed that transforming growth factor-beta1 (TGF-β1) could effectively suppress HBV replication at physiological concentrations. Here, we provide more evidence that TGF-β1 specifically diminishes HBV core promoter activity, which subsequently results in a reduction in the level of viral pregenomic RNA (pgRNA), core protein (HBc), nucleocapsid, and consequently suppresses HBV replication. The hepatocyte nuclear factor 4alpha (HNF-4α) binding element(s) within the HBV core promoter region was characterized to be responsive for the inhibitory effect of TGF-β1 on HBV regulation. Furthermore, we found that TGF-β1 treatment significantly repressed HNF-4α expression at both mRNA and protein levels. We demonstrated that RNAi-mediated depletion of HNF-4α was sufficient to reduce HBc synthesis as TGF-β1 did. Prevention of HNF-4α degradation by treating with proteasome inhibitor MG132 also prevented the inhibitory effect of TGF-β1. Finally, we confirmed that HBV replication could be rescued by ectopic expression of HNF-4α in TGF-β1-treated cells. Our data clarify the mechanism by which TGF-β1 suppresses HBV replication, primarily through modulating the expression of HNF-4α gene

Control Strategy Of Pcdd/Fs In An Industrial Fluidized Bed Incinerator Via Activated Carbon Injection

The emissions of a full range of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) from incinerators have become a significant issue in both aspects of environmental and public health protection. Fluidized bed incinerators (FBI) have been widely used as a typical technology for industrial waste treatment in recent years, especially in the petrochemical industry in Japan, Germany, and Taiwan. In response to public concerns, the Environmental Protection Administration (EPA) in Taiwan had proposed strict limits on the emissions of PCDD/Fs for both industrial and municipal incinerators. The emission standard is 0.1 ng/Nm3, expressed as the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent of 17 specific dioxins and furans congeners. These limits will potentially influence technology selection and design in combustion processes, energy recovery options, and air pollution control devices. Since fluidized bed incinerators with revolving type combustors have been continuously popular in Taiwan for handling industrial sludge, spent oils, and solid wastes, an interesting exercise is to compare the stack concentrations against the proposed standard of concentrations of dioxins and furans (i.e., 0.1 ng/Nm3 TCDD TEQ (toxicity equivalence) and search for a more cost effective way to improve the control strategy. Research findings in this article confirm that the formation and emissions of PCDD/Fs, prior to particulates control device, exhibit a substantial positive correlation with CO concentration in the flue gases. Without using the technique of activated carbon injection to reduce the emissions of PCDD/Fs, the revolving type FBI cannot comply with the emission standards of PCDD/Fs required in Taiwan

Synthesis And Characterization Of Titania Nanotubes For Dye Wastewater Treatment

This paper starts with the preparation of anatase titania nanotube (TN) in large quantities by hydrothermal routes with different calcination temperatures, and then delves into a thorough investigation for the characterization of fine structures or formation mechanism of TN. Experimentally, anatase TiO2 nanoparticle was used as a precursor for TN synthesis. The results showed that the length and diameter of TN range are 50-100 nm and 10-15 nm, respectively. The XRD patterns and BET isotherms indicated that TN owns anatase-typed structures with a surface area of 292m2 /g. By extended X-ray absorption fine structure (EXAFS) spectra, the valency and framework of TN are Ti (IV) with octahedral structures. The EXAFS data also revealed that TN has a first shell of Ti-O bonding with bond distances of 1.95 Å and coordination numbers were 2. The results revealed that the TiO2 anatase nanoparticles can be solved into layer under strong alkaline. The layer of TN further curling itself to reduce the energetics was postulated and found. For calcination temperature larger than 400°C, the microstructure of TN might transform from nanotube into nanoparticles accompanying with the sharp increase for the nanoparticle crystalline phase. With the understanding of pore structure variation on the basic dye (Basic Green 5 (BG5)), the adsorption ability, mechanisms, and kinetics of (Basic Green 5 (BG5)) dye onto TN were examined as well. © World Scientific Publishing Company